Inductance



March 26, 1929. F, A W$ 1,706,991

INDUCTANCE Filed Jan. 11, 1926 Patented Mar. 26, 1929.

UNITED STATES PATENT OFFICE.

EDWARD I. ANDREWS, OF CHICAGO, ILLINOIS, ASSIGNOR TO RADIO CORPORATION OF AIERICA, A CORPORATION OF DELAWARE.

INDUCTANCE.

Application filed January 11, 1928. Serial No. 80,660.

My invention relates to an inductance device for use as an element in a radio receiving set, or other high frequency apparatus. Itis desirable that inductances feruse in. radio frequency circuits have low distributed capaclty and low resistance, but that the shall have a large inductance relative to t e distributed capacity and resistance, and that they occupy a small space. M structure possesses advanta es as to all 0 the foregoing features, and 1n addition thereto is simple and inexpensive to manufacture, sturdy in structure, and convenient in form.

In general, my invention comprises a pluthe wires forming the inductance being wound in the slots in said plates and forming a plurality of spaced pancakes, each one wire in thickness, the outer layer of wire on each pancake being connected to the inner layer of wire on the adjacent pancake where several pancakes are comprised within the same winding on the inductance. Each inductance device may include several windings, which may, if desired, comprise one or more pancakes. The plates upon which the wire is wound may-be radially sup orted about one or more central insulating iscs, or the discs may be omitted, the slotted insulating lates 0. serving as separators to keep the panca es 1n proper spaced relation. In the latter case the pancakes are preferably fixed to the plates by a small amount of some adhesive insulating material, and one of the slotted plates may serve also'as a support.

I It has been found that the form of inductance herein described is vastly more efficient when stranded wire, in which each strand is separately insulated from the other strands, is employed. By the use of a wire composed of a number of relatively small conductors, each one covered with a coating of insulating enamel or with a layer of silk, cotton, or similar material, the high frequency resistance of a coil composed of a number of flat pancakes, axiall spaced, can be very greatly reduced. This orm of construction makes it possible to confine a coil of relatively high inductance 'to a much smaller space than with the conventional single layer cylindrical winding. Although the resistance of the coil of my invention. is higher than the resistance of an equivalent single layer cylindrical coil of the same inductance when solid wire is em loyed, the use of insulated stranded wire wi l efiect rality of slotted plates of insulating material,-

a reduction in the resistance of my coil below that of a conventional type, at least at frequencies corresponding to 400 or 500 meter wave lengths. The distributed capacity of my coil is also lower than that of the cylindrical type, unless the windings are spaced. The difference between the high frequency resistance of the conventional coil using solid or insulated stranded wire is not great, in fact, most authorities recommend the use of solid wire in preference to stranded insulated wire when it is desired to cover the present band of frequencies employed for broadcasting. On the contrary, the superiority of my inductance, when wound with stranded insulated wire as compared with the same coil wound with solid wire, is tremendous.

My invention is illustrated in the accompanying drawings, in which,

Figure 1 is aside elevation of an inductance;

Figure 2 is an end elevation thereof;

Figure 3 is a side elevation of a modified form of an inductance;

Figure 4 is an end elevation thereof;

Figure 5 is one of the slotted plates used in the modification shown in Figures 3 and 4.

In the modification shown in Figures 1 and 2, the slotted insulating plates 26 are clam ed in the coil winding machine, and the con uctor 27 of the primary and the conductor 28 of the secondary winding are wound in the slots in the same manner as previously described.

The conductors 27 and 28 preferably consist of an insulated stranded wire in which each strand is separately insulated, and inasmuch as the pancakes must be practically self-supporting, the Wire is coated with an insulating adhesive material so that each pan cake is rigid and fixed in the slots of the insulating plates 26. The adhesive may be any well known preparation suitable for this purpose. The lower slotted plate 29 is, lar er than the plates 26 so as to provide a suita le mounting for the edestal brackets 30, for the terminals 31 and 32 of the primary winding 27, and for the terminals 33-and 34 of the secondary winding 28. 1 r

In the modification illustrated in Figures 3, 4 and 5, the construction is in most respects 1 5 similar to that shown in Figures 1 and 2 and similar reference characters have therefore been used to designate similar parts.

Figure 5 shows one of the slotted plates 35, which, as used in this modification, are 110 preferably stamped from a thin sheet of cellu loid or similar material. A. suthcient number of these thin sheets, which tor the sake of consistency may be called plates, are provided, so that, in winding the inductance, the coil will be substantially circular. In the manufacture of this inductance, the plates are, as in the above-mentioned modification, clamped in the winding machine, and the wire conductor wound in the slots and fixed in position with a suitable binding material, As soon as the binding material has hardened, the clamps holding the plates may be removed, and it will be found that the inductance is sutficiently strong and rigid so that it may be easily packed and shipped, or roughly handled, without danger of it getting out of shape.

Some of the advantages which are realized in common from. the above described embodiments of my invention are:

First: The construction facilitates winding the adjacent pancakes on the same coil all from the inside of the slots to the outside thereof, so that the conductors of adjacent pancakes which have the greatest difierence of potential will lie the greatest distance apart; that is, at the bottom of one slot and the top of the adjacent slot.

Second: An inductance wound in this manner has an. advantageous space insulation resulting from the fact that the various pancakes of turns are spaced from one another with air separation, except at a few intervals Where the windings contact with the thin edges of the dielectric.

Third: A very small amount of dielectric material lies in contact with the conductors, and that which is spaced away from the conductors is located in a comparatively low electrostatic field,

Fourth: The arrangement facilitates the construction of a given inductance having very low distributed capacity and resistance confined within a small space and one which needs no lacquer or other binding dielectric coating for providing the necessary strength to hold the inductance in shape.

The inductances shown have the especial advantage that the shin efiect is greatly reduced by the use oi the stranded wire in which each strand separately insulated.

The inductance shown. in Figures 3, 4 and 5 has the additional. advantage of light weight, strength, and small area of contact between the coils and the dielectric.

means-i Having thus described my invention and the advantages thereof, I desire it to be understood that the same advantages may be gained through slight variations and modifications in the construction, lying within the scope of my invention What I claim is:

1. An inductance device comprising a wire, a plurality of plates of insulating material, each plate having a series of parallel slots wide enough to frictionally engage the wire, said plates being spaced from each other with their corresponding slots in alignment, said wire being wound in said slots to form pancake coils, said wire trictionally engaging the sides of the slots, forming the sole support for said plates, and holding said plates in spaced position, one of said plates serving as a support for the device.

2. In an inductance device comprising primary and secondary coils, a plurality of radially extending plates, each plate having a plurality of outwardly extending parallel slots, a conductor of stranded wire, each strand of which is separately insulated, the slots in said plates being aligned and of a width suthcient to allow frictional engagement with said conductor, the conductor being wound with one convolution directly above the adjacent convolution of each. slot and from the top of one slot to the bottom of the next slot, terminal posts on one of said plates, and mounting means secured to one of said plates, whereby one plate supports the entire device and all the remaining plates and coils are maintained in their fixed relative position by virtue of the frictional engagement of the coils in the slots.

3. An inductance device comprising a conductor, a plurality of spacing plates, each plate having a plurality of parallel slots therein wide enough to permit the conductor to be wound therein and narrow enough to prevent contiguous turns of the conductor from lying side by side in the slot, said plates being spaced from each other with their corresponding slots in alignment, said conductor being wound in said slots to form pancake coils, means for securing the convolutions oi the conductor to said plates, whereby said conductor forms the sole support for said plates and holds them in spaced position, and means for mounting the device.

In witness whereof, I hereunto subscribe my name this 9th day at January, 19%.

EDWARD l3. ANDREWE.

till 

